Lateral Bipolar Transistor Base Layout for Larger Interface Area

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Solution Overview

Problem

Conventional bipolar transistors, such as vertical bipolar transistors, often have higher costs and operational parameters that do not meet certain constraints, limiting their electrical behavior and performance in integrated circuits.

Innovation Solution

A lateral bipolar transistor structure is designed with an emitter/collector layer on a semiconductor layer, featuring a first base layer with varying horizontal widths and a second base layer adjacent a spacer, where the upper portion of the first base layer separates the lower surface of the second base layer from the emitter/collector layer, optimizing the physical interface and conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional vertical bipolar transistors are used, then the device structure is simple and manufacturing is easier, but the operational parameters do not meet certain constraints and electrical behavior is limited

Engineering Contradiction:

Improveelectrical behaviorVSAvoidtransistor structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent transitions from a vertical bipolar transistor configuration to a lateral configuration, changing the spatial arrangement of emitter, base, and collector regions from vertical stacking to horizontal positioning. This dimensional change enables improved electrical behavior and operational parameters while maintaining compatibility with standard CMOS processing techniques

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Area of stationary object

If the base layer has uniform width, then the manufacturing process is simpler, but the physical interface area between base and emitter/collector is limited

Engineering Contradiction:

Improvephysical interface areaVSAvoidbase layer geometry

Core Design Contradiction:

Area of stationary objectVSDevice complexity

Solution Approach 1:

The base layer is designed with non-uniform width, featuring a wider upper portion and a narrower lower portion. This local variation in geometry increases the physical interface area between the base and emitter/collector layers at the upper portion, thereby improving electrical behavior without requiring complete structural redesign

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The base layer employs a tapered or curved profile rather than a straight vertical sidewall, creating a gradual transition from the wider upper portion to the narrower lower portion. This curved geometry maximizes the lateral interface area while maintaining structural integrity and compatibility with standard fabrication processes

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentUS11908898B2Lateral bipolar transistor structure with base layer of varying horizontal width and methods to form same

Publication Date: 2024.02.20 GLOBALFOUNDRIES US INC

AI summary

Embodiments of the disclosure provide a lateral bipolar transistor with a base layer of varying horizontal thickness, and related methods to form the same. A lateral bipolar transistor may include an emitter/collector (E/C) layer on a semiconductor layer. A first base layer is on the semiconductor layer and horizontally adjacent the E/C layer. The first base layer has a lower portion having a first horizontal width from the E/C layer. The first base layer also has an upper portion on the lower portion, with a second horizontal width from the E/C layer greater than the first horizontal width. A second base layer is on the first base layer and adjacent a spacer. The upper portion of the first base layer separates a lower surface of the second base layer from the E/C layer.